Secondary sexual behavior in Longisquama (and Cosesaurus)

Sure Longisquama had giant plumes
that likely entranced the lay-dees… and/or the gents…

But as the proximal outgroup to the Pterosauria,
and provided with a similar pectoral girdle (sternal complex, strap-like scapulae, quadrant-shaped coracoids, it was a likely flapper, as we talked about earlier here with similar traits in Cosesaurus (Fig. 1)

Figure 1. Cosesaurus flapping - fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

Figure 1. Click to enlarge and animate. Cosesaurus flapping.

Here (Fig. 2) is an animated Longisquama, flapping and with tail wags, which we talked about earlier here.

Figure 2. Click to animate. Longisquama flapping and wagging its tail.

Figure 2. Click to animate. Longisquama flapping and wagging its tail.

With these traits and behaviors basal fenestrasaurs converged with theropods ancestral to birds. In these ways flapping preceded powered flight, in both cases co-opted from secondary sexual behaviors in these highly visual reptiles.

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Cartorhynchus: not an ichthyosaur, not amphibious and not a sucker

Earlier (in early November 2014) we looked at the new discovery of Motani et al. (2014), Cartorhynchus (Fig. 1), which they recovered as an ichthyosaur ancestor, amphibious and a suction feeder. The paper was officially released by Nature (Motani et al. 2015) recently, hence the redux here.

Unfortunately
Like the Holy Roman Empire, Cartorhynchus is neither an ichthyosaur, amphibious nor a suction feeder.

Figure 1. Although the pectoral girdle was preserved just behind the skull, in all sister taxa there are about 19 cervicals and 19 dorsals. Plus the pectoral girdle itself is very wide, better suited to the widest ribs. Perhaps Cartorhynchus had a longer neck than commonly assumed.

Figure 1. Although the pectoral girdle was preserved just behind the skull, in all sister taxa there are about 19 cervicals and 19 dorsals. Plus the pectoral girdle itself is very wide, better suited to the widest ribs. Perhaps Cartorhynchus had a longer neck than commonly assumed.

Not an ichthyosaur
1. The large reptile tree, now up to 484 taxa, nests Cartorhynchus as a basal sauropterygian, between Pachypleurosaurus and Qianxisaurus. That’s why Cartorhynchus has a short snout, like its sisters, unlike the long snout in Wumengosaurus, hupehsuchids and ichthyosaurs. A large suite of traits separates Cartorhynchus from ichthyosaurs. Shifting Cartorhynchus to the base of the ichthyosaurs adds 33 steps.

Not amphibious
2. That tiny neck, tiny cervical ribs and giant head (Fig. 1) strongly indicate that life above the water would be very difficult indeed. Then there’s a lack of ossified phalanges as the limbs turn into rather soft flippers. Then there’s the shortening of the limb bones and a lack of elbows and knees. Ironically, Cartorhynchus was less amphibious than its sister taxa, Pachypleurosaurus and Qianxisaurus. Then there’s the flat ventral surface, perfect for bottom dwelling underwater. Nothing but [a] drag on land.

Not a suction feeder
3.  Suction feeders, like seahorses, can have a tiny mouth, unable to open much. On the other hand, the mata mata turtle does not have a tiny mouth, but it does have a long neck and a strong hyoid apparatus, which quickly expands the neck creating the suction of water that impels prey back to the throat. Suction feeders also tend to lose their teeth. Cartorhynchus, but contrast, has a wide gape and large teeth, despite its pincer like premaxilla. The high coronoid process and large temporal fenestra indicate large jaw muscles were present, perfect for biting, unnecessary for suction feeding. There is no great hyoid apparatus here and no long neck for the water to rush into.

References
Motani R et al. 2014. A basal ichthyosauriform with a short snout from the Lower Triassic of China. Nature doi:10.1038/nature13866
Motani R, Jiang D-Y, Chen G-B, Tintori A, Rieppel O, Ji C & Huang J-D 2015. A basal ichthyosauriform with a short snout from the Lower Triassic of China. Nature 517: 485–488. doi:10.1038/nature13866

http://www.nature.com/
wiki/Cartorhynchus

Manus dominated pterosaur tracks from Early Cretaceous, Gansu, China

A recent paper by Li et al. (2015)
reveals a manus dominated pterosaur trackway associated with minor sandstones in the mud-dominated sequence in the Hekou Group, Gansu, China. They report the tracks are mostly random and “likely reflect differential registration depths of manus and pes and/or sub optimal preservation conditions.”

How long will the alternate explanation be ignored?
We’ve got a better explanation for manus-dominated tracks (Fig. 1). Pterosaurs could float and pole themselves around using their hands (but see below!). Not sure why this alternate explanation continues to be avoided. It also explains the randomness of the tracks. The pterosaurs were rotating above the beds of bottom-dwelling menu items.

Figure 1. The azhdarchid pterosaur Quetzalcoatlus floating and poling producing manus only tracks.

Figure 1. The azhdarchid pterosaur Quetzalcoatlus floating and poling producing manus only tracks.

The authors did not match a specific trackmaker to the tracks (see below) despite having all the clues necessary to do so (Fig. 2). The manus is about the length of the pes. The pes is extremely narrow with pedal digits 1-4 about equal in length and pedal digit 5 is a vestige at best. The time is Early Cretaceous. The place is China. Jidapterus, a protoazhdarchid, is a good match (Peters 2011).

Figure 2. Jidapterus matched to the Gansu, Early Cretaceous pterosaur tracks. The trackmaker was one-third larger than the Jidapterus skeleton.

Figure 2. Jidapterus matched to the Gansu, Early Cretaceous pterosaur tracks. The trackmaker was one-third larger than the Jidapterus skeleton. 

Invertebrate traces and burrows
are found throughout the track strata providing a good clue to azhdarchid and protoazhdarchid diets. These were probing pterosaurs, picking up burrowing invertebrates with they long beaks (Fig. 3). Not scavengers….Not baby dinosaur predators.

Quetzalcoatlus scraping bottom while standing in shallow water.

Figure 3. Quetzalcoatlus scraping bottom while standing in shallow water.

The first pterosaur tracks reported from China (Peng et al. 2004, Zhang et al. 2006, Fig. 4 ) represent a single individual slightly larger than the Gansu trackmaker actually making a directed track. By the dimensions and shape, this trackmaker was likely also a Jidapterus-like azhdarchid.

Figure 4. The Yanguozia No. 1 pterosaur track compared to the Jidapterus trackmaker. Note the presence of pedal digit 5 in the track as note by the authors.

Figure 4. The Yanguozia No. 1 pterosaur track compared to the Jidapterus trackmaker. Note the presence of pedal digit 5 in the track as note by the authors. From Zhang et al. 2006.

Li et al. report,
“The small sample size also makes it difficult to discern systematic features across a significant number of tracks, so the material is referred to only as Pteraichnus isp.” That’s a shame because I was able to identify the trackmaker within minutes. It’s not that hard given the clues and resources, like “the catalog of pterosaur pedes for trackmaker identification” (Peters 2011). I mean…that’s why I wrote and illustrated it, just for cases like this.

Li et al. report,
“The lack of pes tracks, predominance of, or greater depth of manus tracks at many pterosaur track sites could reflect the greater proportion of body weight (relative to foot surface area) born by the pterosaur forelimbs.”
Then they go the other way, “However, this manus-emphasis trait may also depend on substrate consistency. For example, in specimens of Pteraichnus isp. from the Wenxiyuan tracksite, Shandong Province, the pes impressions are as deep or deeper than the manus impressions.” 

Li et al dismiss the floating hypothesis
by reporting, “The random distribution of the deep tracks could perhaps indicate that the pterosaurs were semi-floating and making irregular contact with bottom of a non-marine shallow-water environment. However, we consider this unlikely, given the remnants of typical walking trackway configurations.” Pterosaurs weren’t jumping into the pool. They were walking in from the shore.

They also reference Hone and Henderson who, “employed digital models to imitate the swimming strokes of pterosaurs, and their results suggest that many pterosaurs did not regularly rest on the surface of the water and, if immersed, would need to take off rapidly.” That paper and its hypotheses were thoroughly debunked here.

Li et al. reference Lockley et al 2014
when they report, “It is possible that buoyant or semi-floating pterosaur trackmakers touched the substrate with their forelimbs, while their shorter hindlimbs floated and perhaps paddled in the water above. This would require deliberately lowering the wrist to the substrate, below the level reached by the feet, and thus, as noted below, seems like an improbable interpretation. Much track evidence suggests that the reverse was typically the case: i.e., swim track assemblages usually show only the traces of hind footprints, mostly with associated elongate drag or scratch marks [Lockley et al. 2014]. In such cases, this indicates water depths were roughly equal to the length of the pterosaurs’ legs. Given that it is known that pterosaur manus tracks are often deeper, more common and thus more easily preserved than pes tracks, in non-swim track assemblages, it is most parsimonious to infer that the irregular to random distribution of many of the manus tracks at the Yangouxia pterosaur tracksite are most simply explained by variable preservation. Pterosaur tracks are typically associated with shorelines and shallow water and are often represented by quite high-density assemblages with variable combinations of manus and pes tracks. Thus, while we cannot discount the possibility that some manus tracks are associated with swimming trackmakers, this cannot be proven, and it is more parsimonious to infer that the irregular distribution patterns are the result of variable preservation.” This is an odd sort of logic IMHO. Variable preservation? Manus only tracks were somehow selected by geological factors (see Fig. 6)? That doesn’t make sense over one instance, let alone several now known worldwide.

Lockley et al. 2014 Dakota Group tracks
Lockley et al. attribute long scratch marks to pterosaurs (Fig. 5) and this may be so.

Dakota Group pterosaur swimming tracks preserved as long scratches in the substrate. The best matches for size, time and morphology are the shenzhoupterids through the tapejarids. These are a different sort of pterosaur than the Gansu trackmaker, Jidapterus.

Figure 5. Dakota Group pterosaur swimming tracks preserved as long scratches in the substrate. The best matches for size, time and morphology are the shenzhoupterids through the tapejarids. These are a different sort of pterosaur than the Gansu trackmaker, Jidapterus.

If so,
in morphology and size they represent a different sort of pterosaur than the Gansu trackmaker. The Dakota Group trackmakers from the Mid Cretaceous appear to be most closely related to Shenzhoupterus, Sinopterus, Tapejara and Tupuxuara, of which, based on the small claw size, Shenzhoupterus appears to be the closest match. We looked at Tapejara floating and swimming earlier here.

Feeding hypotheses
Lie et al. report, “The association of the Y-PS1-2 tracks with abundant invertebrate ichnofossils (P. tubularis)  raises the possibility that the pterosaurs were feeding on the invertebrate trackmakers. There are many sites where pterosaur tracks occur with invertebrate traces and Lockley and Wright reported such associations in the late Jurassic of the western USA and Garcia-Ramos et al. [52] reported pterosaur footprints associated with Lockeia at the Tazones tracksite, in Asturias (northern Spain). However, there is no feeding trace that has been observed on these pterosaur tracks surface, probably due to the preservation or the special feeding way (such as filter feeding of ctenochasmatids).” Actually little peck marks might be present. Hard to tell in the invertebrate burrow beds.

Trackmaker candidates according to Li et al. 
Li et al. could not rule out a non-pterodactyloid trackmaker because the impression of “pedal digit V is rarely impressed clearly and unambiguously.”  They consider dsungaripterids and Huanhepterus (hands not known, feet only figured in lateral view in the literature) without considering azhdarchids, like Jidapterus, and without referencing the catalog of pterosaur pedes for trackmaker identification (Peters 2011).

How pterosaurs produced manus only tracks
has been illustrated by Mark Witton (Fig. 6, from Li et al. 2014). I only hope he was squirming when he did this, as it defies all logic. Note the sediment behind the walking pterosaur is not preserving its pedal tracks. Nor are the manus only tracks random.

This is bad science: rejecting great solutions and publishing magic (hind limb levitation) or selective geology (harder and less compliant matrix only beneath the pedes). Evidently whenever my views are considered that appears to ‘poison the waters’ so any other solution, no matter how bizarre, is embraced. That’s too bad that it has come to this.

Figure 6. Illustration by Mark Witton showing how pterosaurs could walk on mudflats without leaving pedal imprints. If you understand the logic behind this image, please write to me.

Figure 6. Illustration by Mark Witton showing how pterosaurs could walk on mudflats without leaving pedal imprints. If you understand the logic behind this image, please write to me. Note these tracks are not random, but follow the walking path. On the positive side, nice to see the narrow chord wing membranes here. Has Witton adopted this configuration?

References
Hone DWE, Henderson DM 2014. The posture of floating pterosaurs: Ecological implications for inhabiting marine and freshwater habitats. Palaeogeography, Palaeoclimatology, Palaeoecology 394:89–98.
Li D-Q, Xing L-D, Lockley MG, Piñuela L, Zhang J, Dai H, Kim J Y, Persons S and Kong D 2015. A manus dominated pterosaur track assemblage from Gansu, China: implications for behavior. Science Bulletin 60(2):264-272.
Lockley MG, Cart K, Martin J et al 2014. A bonanza of new tetrapod tracksites from the Cretaceous Dakota Group, western Colorado: implications for paleoecology. New Mexico Museum of Natural History Science Bulletin 62:393–409
Peng BX, Du YS, Li DQ et al. 2004. The first discovery of the Early Cretaceous pterosaur track and its significance in Yanguoxia, Yongjing County, Gansu Province. J Chin Univ Geosci (Earth Sci) 29:21–24.
Peters D 2011. A catalog of pterosaur pedes for trackmaker identification. Ichnos 18(2):114-141.
Zhang JP, Li DQ, Li M et al. 2006. Diverse dinosaur-, pterosaur-, and bird-track assemblages from the Hakou Formation, Lower Cretaceous of Gansu Province, northwest China. Cretaceous Research 27:44–55.

Skulls at the Protodiapsid/Synapsid Split

Updated February 23, 2015 with a new image of Mycterosaurus.

Earlier we looked at taxa at the Protodiapsid/Synapsid split. Here’s an update with skulls alone after the addition of two Protorothyris skulls (Fig. 1).

Figure 1. Reptile skulls at the protodiapsid/ synapsid split to scale with Protorothyris as the proximal outgroup. Note the elongation of the rostrum and the appearance of the the lateral temporal fenestra. The two clades were originally quite similar. Two versions of Mycterosaurus are shown. Click to enlarge.

Figure 1. Reptile skulls at the protodiapsid/ synapsid split to scale with Protorothyris as the proximal outgroup. Note the elongation of the rostrum and the appearance of the the lateral temporal fenestra. The two clades were originally quite similar. Two versions of Mycterosaurus are shown. Click to enlarge.

Descending from a sister
to Coelostegus, Protorothyris (Fig. 1) nests as the proximal outgroup to the split between the Synapsids and Protodiapsids (which gave rise to the Diapsida). The narrower skull of the more derived MCZ 2149 specimen of Protorothyris continues in both clades. The relatively short rostrum of the MCZ 2149 specimen of Protorothyris was an autapomorphy.

Both protodiapsid and synapsid clades display 

  1. a new lateral temporal fenestra (with concurrent temporal bone shape changes)
  2. a longer rostrum
  3. longer ascending process of the premaxilla
  4. the maxilla was at least as deep as the lacrimal
  5. the pineal opening was larger
  6. the frontal was not so narrow
  7. the supratemporal contacted the postorbital
  8. the cervical ribs were not robust and parallel to the centra
  9. metatarsal 1 was less than half of metatarsal 3
  10. pedal 5.1 did not extend beyond metatarsal 4

In basal protodiapsids

  1. the naris was ventrally bordered by the maxilla chiefly.
  2. the maxilla expanded dorsally, blocking contact between the lacrimal and naris, but only in the Heleosaurus/Mycterosaurus/Mesenosaurus clade. Other protodiapsids and basal diapsids did not have his trait.
  3. the naris was elongated
  4. the nasals and frontals were subequal
  5. the basipterygoid processes were prominent
  6. retroarticular process descended
  7. cervical neural spines were not taller than the centra
  8. medially the clavicles were not broad
  9. the coracoid, even when fused, was larger than the scapula
  10. the radiale and intermedium were elongated
  11. the radius and ulna were together longer than 3x their width
  12. the tibia is not less than twice the ilium length

In basal synapsids

  1. the naris is ventrally bordered by the premaxilla ventrally.
  2. most of this clade had nasals longer than frontals
  3. most taxa had a convex ventral maxilla (but so did Helosaurus).
  4. the occipital was anterior to the jaw joint
  5. broader supraoccipital
  6. mandible tip rises
  7. retroarticular process rises
  8. transverse processes appear on the vertebrae
  9. the manus and pes were subequal
  10. the ilium is longer than tall
  11. the pelvic elements are fused
  12. pedal 4.1 is shorter than three times its width
  13. overall length longer than 30cm

This phylogenetic split has not been recognized in academic literature as generic diapsids are rarely to never tested with basal synapsids.

References
Clark J and Carroll RL 1973. Romeriid Reptiles from the Lower Permian. Bulletin of the Museum of Comparative Zoology 144 (5): 353-408 .
Price LI 1937. Two new Cotylosaurs from the Permian of Texas: Proceedings of the New England Zoological Club, v. 16, p. 97-102.
wiki/Protorothyris

Stephen Czerkas

Paleoartist and writer Stephen Czerkas died this week.
I respected his artwork (Fig. 1). He was 63 years old.

Stephen Czerkas paleoartist with his most famous creation, before and after feathers.

Figure 1. Stephen Czerkas paleoartist with his most famous creation, Deinonychus, before and after feathers.

I only met Stephen Czerkas once, 
but saw his famous Deinonychus everywhere. He and his wife Sylvia were at or near the center of dinosaur reconstruction several decades ago when I was just a pup. They published several books. Opened a museum. Introduced the world to sauropod spines and made some bad decisions.

Stephen Czerkas was a serious worker, intent on ‘getting things right.’ To that end he added feathers to his Deinonychus (Fig. 1).

Sorry to see him go. He influenced us all.

Learn more here from Bill Stout’s homage to Stephen Czerkas.

 

Baurusuchus, the land croc with a tyrannosaur-like skull

Figure 1. Baurusuchus, the two species is a land croc related to notosuchians.

Figure 1. Baurusuchus, the two species is a land croc related to notosuchians. Click to enlarge. Note the large shoulder spines, short torso, short tail and long legs.

Baurusuchus salgadoensis (Price 1945, Souza Carvalho et al. 2005, Nascimento and Zaher 2010, Late Cretaceous) was a large (3.5 m, 11 ft) terrestrial predator. Rather than having a low wide snout, Baurusuchus had a tall narrow rostrum, like rauisuchians of the Triassic, a trait shared with Caipirasuchus (see below). The teeth were robust, laterally compressed and serrated. Vertebral spines over the shoulders were very tall. The tail was relatively short. The coracoid was as long as the scapula.

Distinct from most living crocs, this one lived in a hot and arid climate. Baurusuchus would have ambushed its prey, biting deeply then releasing and waiting for its prey to die of blood loss, hoping that a passing giant abelisaurid theropod would not steal its meal.

Figure 2. Caipirasuchus is a much smaller land croc, a notosuchian with a tall narrow skull.

Figure 2. Caipirasuchus is a much smaller land croc, a notosuchian with a tall narrow skull.

According to the large reptile tree, among the few crocs that are included (many more are known, but not yet included, Fig. 3), a notosuchian with a similarly narrow skull, Caipirausuchus stenognathus, (Pol et al. 2014, fig. 2) nests as a perhaps distant sister taxon.

Notosuchian crocodyliforms were extremely diverse in the Cretaceous of South America. Notosuchians are usually characterized by heterodont dentition.

Sebecus, another narrow-rostrum croc nests (Fig. 3) with living crocs and the ancestor of all living crocs, Isisfordia.

Figure 3. Archosaur family tree focusing on basal crocodylomorphs with Bootstrap scores.

Figure 3. Archosaur family tree focusing on basal crocodylomorphs with Bootstrap scores.

References
de Souza Carvalho I, de Celso Arruda Campos A and Nobre PH 2005. Baurusuchus salgadoensis, a New Crocodylomorpha from the Bauru Basin (Cretaceous), Brazil. Gondwanta Research 8:11-30.
Nascimento PM and Zaher H 2010. A new species of Baurusuchus (Crocodyliformes, Mesoeucrocodylia) from the Upper Cretaceous of Brazil, with the first complete postcranial skeleton described for the family Baurusuchidae. Paéis Avulsos de Zoologia. Museu de Zoologia da Universidade de São Paulo. 50(21):323-361. online pdf
Pol D, Nascimento PM, Carvalho AB, Riccomini C, Pires-Domingues RA and Zaher H 2014. A New Notosuchian from the Late Cretaceous of Brazil and the Phylogeny of Advanced Notosuchians. DOI: 10.1371/journal.pone.0093105
Price LI 1945. A new reptile from the Cretaceous of Brazil. Departamento Nacional da Produção Mineral, Notas preliminares e estudos (Rio de Janeiro) 25:1–8.

wiki/Baurusuchus

What is Orientognathus? Nesting via description, not observation

Orientognathus chaoyngensis (Lü et al. 2015) is a new Late Jurassic rhamphorhynchoid pterosaur known at present from a series of comparative descriptions. No illustration or photograph of the incomplete(?) material is yet known (at least to me at present).

Given these limitations, let’s see how close we can nest this new enigma.

Data provided:

  1. toothless tip of dentary, slightly pointed
  2. mc4/humerus ratio = 0.38
  3. ulna < each individual wing phalanx
  4. tibia subequal to femur
  5. deltopectoral crest more developed than in Qinlongopterus
  6. anterior teeth stouter and longer than in Pterorhynchus
  7. teeth are straight and longer than in Jianchangnathus
  8. pteroid/humerus ratio = 0.21; pteroid has expanded distal end
  9. larger than other rhamphorhynchine pterosaurs from Late Jurassic NE China (measurements not indicated).

Evidently there is not much known of this specimen:
jaw tips and teeth, a pteroid, a humerus, an ulna, a metacarpal 4, a complete (?) wing (doubtful because the phalanx ratios are not compared to one another) and a femur are all that are mentioned here.

Step one: tibia = femur:
In almost all pterosaurs the tibia is longer than the femur. Just a few specimens have this odd sub equal ratio, so that winnows down the long list of pterosaurs to a short list of possible candidates (left me know if I overlooked any other candidates). You can click the name to view the reconstruction.

  1. Rhamphorhynchus gemmingi? MYE 13 (von Meyer 1859, No. 75 in the Wellnhofer 1975 catalog)
  2. Scaphognathus ( 2 specimens)
  3. St/Ei I (JME 1)

Step two: ulna < each individual wing phalanx
That trait removes both specimens of Scaphognathus and the St/Ei (JME 1) specimen, leaving only one candidate.

Step three: A closer look at Rhamphorhynchus MYE 13 (Fig. 1).

  1. Toothless tip of dentary, slightly pointed: Yes.
  2. mc4/humerus ratio = 0.38  No. = 0.50, but then MYE 13 has a relatively shorter humerus than most Rhamphorhynchus specimens.
  3. ulna < each individual wing phalanx Yes
  4. tibia subequal to femur  Yes
  5. deltopectoral crest more developed than in Qinlongopterus Yes
  6. anterior teeth stouter and longer than in Pterorhynchus Yes
  7. teeth are straight and longer than in Jianchangnathus Yes
  8. pteroid/humerus ratio = 0.21 (but is the pteroid complete?); No. In MYE 13 the ratio is 0.66, but, as above, the humerus is atypically short  AND pteroid has expanded distal end  Yes
  9. Larger than other rhamphorhynchine pterosaurs from Late Jurassic NE China
    Maybe. Wing fingers in Rhamphorhynchus specimens are relatively larger than are those in other Late Jurassic pterosaurs, so if only a wing is known it could belong to a relatively smaller skull and torso. Otherwise the mid-sized specimens listed above (except tiny Qinlongopterus) are all about the same size. 
Figure 1. The MYE 13 specimen of Rhamphorhynchus (n75 in the Wellnhofer 1975 catalog is currently the closest match to the Orientognathus description.

Figure 1. The MYE 13 specimen of Rhamphorhynchus (n75 in the Wellnhofer 1975 catalog is currently the closest match to the Orientognathus description.

So, we’ll test these hypotheses
when the images become available, hopefully with scale bars. Then we’ll do a comparison.

References
Lü J-C, Pu H-Y, Xu L, Wei X-F, Chang H-L and Kundrát M 2015. A new rhamphorhynchoid pterosaur (Pterosauria) from Jurassic deposits of Liaoning Province, China. Zootaxa 3911 (1): 119–129.  http://dx.doi.org/10.11646/zootaxa.3911.1.7